MCC Generations (Waterloo Generations) and Value Village have a bigger variety in selection for both males and females. Talize (1144 Courtland Ave E Kitchener) is my favourite of the the larger second-hand stores locally (albeit out of the way from UW).

If you are more lady-inclined with your clothing shopping definitely check out these on King St. in Kitchener:

White Tiger (very cool)

Out of the Past

Delirium

(The last two are a little more counter-culture punk which you may not be into, but still, all great selection for females. Males, not so much)

It also really depends on what you're looking for. The bigger stores that I mentioned first are great for tacky find (i.e. costume parties), but can be hard to find a real keeper. However, as mentioned, the boutiques on King are trendy but sell mostly girls' clothing and can be more pricey.

not so close to campus, youd need a car, but Talize on Courtland in kitchener is awesome. best variety ive ever seen, and it doesnt smell as musty as other thrift stores. my friend found a perfect burberry sweater for $7